BIO_s_core, BIO_new_from_core_bio - OSSL_CORE_BIO functions

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       Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance
       with the License.  You can obtain a copy in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.5.0                                              2025-06-04                                   BIO_S_CORE(3SSL)

BIO_s_core() returns the core BIO method function.

       A core BIO is treated as source/sink BIO which communicates to some external BIO. This is primarily
       useful to provider authors. A number of calls from libcrypto into a provider supply an OSSL_CORE_BIO
       parameter. This represents a BIO within libcrypto, but cannot be used directly by a provider. Instead it
       should be wrapped using a BIO_s_core().

       Once a BIO is constructed based on BIO_s_core(), the associated OSSL_CORE_BIO object should be set on it
       using BIO_set_data(3). Note that the BIO will only operate correctly if it is associated with a library
       context constructed using OSSL_LIB_CTX_new_from_dispatch(3). To associate the BIO with a library context
       construct it using BIO_new_ex(3).

       BIO_new_from_core_bio() is a convenience function that constructs a new BIO based on BIO_s_core() and
       that is associated with the given library context. It then also sets the OSSL_CORE_BIO object on the BIO
       using BIO_set_data(3).

       Create a core BIO and write some data to it:

        int some_function(OSSL_LIB_CTX *libctx, OSSL_CORE_BIO *corebio) {
            BIO *cbio = BIO_new_from_core_bio(libctx, corebio);

            if (cbio == NULL)
                return 0;

            BIO_puts(cbio, "Hello World\n");

            BIO_free(cbio);
            return 1;
        }

BIO_s_core() and BIO_new_from_core_bio() were added in OpenSSL 3.0.

       BIO_s_core, BIO_new_from_core_bio - OSSL_CORE_BIO functions

BIO_s_core() return a core BIO BIO_METHOD structure.

       BIO_new_from_core_bio() returns a BIO structure on success or NULL on failure.  A failure will most
       commonly be because the library context was not constructed using OSSL_LIB_CTX_new_from_dispatch(3).

        #include <openssl/bio.h>

        const BIO_METHOD *BIO_s_core(void);

        BIO *BIO_new_from_core_bio(OSSL_LIB_CTX *libctx, OSSL_CORE_BIO *corebio);